But who killed Woodard and why remained a mystery on Tuesday as police studied security videotape of the unidentified gunman and delved into Woodard's checkered past for clues.

The slaying "was not a random thing as far as we can tell," Mayor Michael Bloomberg said Tuesday.

Jessie Woodard, Woodard’s father, told ABC7 he has no idea why anyone would walk up to his son on a busy New York city street corner and shoot him in the back of the head.

Jessie Woodard said he hadn't spoken to his son in more than a decade. But he knew Brandon had a 4-year-old daughter and lived in the Los Angeles area near his mother. He says he is just shocked about what happened to his son.

“A kid killed like that execution style. I just can't imagine anything like that,” he says.

Friends of Woodard say he was a loving father, was attending law school in California and was in New York visiting friends.

Now Jessie Woodard says he wants desperately to find the man who killed his son in one of the most brazen murders ever committed on the streets of New York City.

Surveillance footage

Seeking the public's help in identifying the shooter, the New York Police Department circulated security camera footage indicating he knew Woodard was in the area - and was waiting for the 31-year-old from Los Angeles.

It shows the gunman, who appears to be bald and have a beard, exit the passenger side of a parked Lincoln sedan about 10 minutes before the shooting on Monday.

He can be seen pulling the hood of his jacket over his head before approaching Woodard. A separate photo shows the gunman reaching into his pocket for a pistol moments before he shot his victim in the back of the head.

The killing occurred on West 58th Street near the Time Warner Center, an area often teeming with car and pedestrian traffic.

After the gunfire, the shooter slipped into the same Lincoln sedan and was driven away. No one else was harmed.

Authorities in Los Angeles and Las Vegas confirmed that Woodard had a history of run-ins with the law in both places. Woodard had been due back in court on Jan. 22 following his arrest by LA County sheriff's deputies in West Hollywood in April on a felony cocaine possession charge.

He had previously pleaded not guilty. Court records show that in December 2009, Woodard pleaded no contest in the Los Angeles suburb of Torrance to a misdemeanor charge of hit-and-run driving.

He was sentenced to three years of probation and a day in jail. However, his probation was terminated in January 2011.

In 2008, he pleaded no contest to two misdemeanor charges of grand theft of property. Prosecutors said he stole items on Feb. 26, 2008, from two upscale markets - a Whole Foods Market and a Gelson's - in Beverly Hills. He was sentenced to nine days of jail and 200 hours of community service.

Woodard also was issued a misdemeanor battery summons in September 2004 after a backstage scuffle with a security officer at a concert at the Mandalay Bay resort on the Las Vegas Strip.

The records show Woodard failed to appear in Las Vegas Justice Court in October 2004 and a warrant was issued for his arrest. He was arrested in April 2008 in Las Vegas, based on the warrant.

After pleading guilty, he was given credit for time served and released.

A spokesman for Loyola Marymount University in Los Angeles said that a student named Brandon Woodard with the same birthday as the victim graduated from the school in 2003 with a bachelor's degree in business administration.